821131382569 has 9 divisors (see below), whose sum is σ = 850449849847. Its totient is φ = 792791134744.

The previous prime is 821131382563. The next prime is 821131382573. The reversal of 821131382569 is 965283131128.

The square root of 821131382569 is 906163.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 430581378969 + 390550003600 = 656187^2 + 624940^2 .

It is not a de Polignac number, because 821131382569 - 2²⁵ = 821097828137 is a prime.

It is a super-2 number, since 2×821131382569² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821131382563) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 26263104 + ... + 26294350.

Almost surely, 2^821131382569 is an apocalyptic number.

821131382569 is the 906163-rd square number.

821131382569 is the 453082-nd centered octagonal number.

It is an amenable number.

821131382569 is a deficient number, since it is larger than the sum of its proper divisors (29318467278).

821131382569 is an frugal number, since it uses more digits than its factorization.

821131382569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62552 (or 31276 counting only the distinct ones).

The product of its digits is 622080, while the sum is 49.

Multiplying 821131382569 by its sum of digits (49), we get a square (40235437745881 = 6343141²).

The spelling of 821131382569 in words is "eight hundred twenty-one billion, one hundred thirty-one million, three hundred eighty-two thousand, five hundred sixty-nine".